In modern building projects, many interior walls are finished with wallboard. Wallboard is manufactured in solid sheets of standard size and may be referred to as drywall, sheet rock, or gypsum board depending on the mixture of materials used to form the solid sheets. Wallboard may be used in buildings having interior walls framed with metal or wooden studs. Wallboard sheets are typically attached to the studs, in adjacent side-by-side relation, to form a flat surface. Joints occurring between adjacent sheets are filled and smoothed to form a wall which appears seamless, at the joints. Joints occurring at wall corners are similarly filled. The walls are finished with a final coat of wall paper or paint.
Joints are typically filled by first applying a layer of paper or mesh tape and second by applying a first coat of joint compound, also referred to as spackle or mud. The joint tape is provided with adhesive, on one surface, for adhering the tape to the wallboard. The tape also retains a quantity of joint compound to prevent the entire joint from filling with joint compound. It is important that the joint compound penetrate the tape so that the joint compound and not the adhesive of the tape adheres to the wallboard, because the adhesive has relatively short effective life. The failure of the bond, in the area of the joint would release the joint tape together with any final coat of paint or wall paper, from the wall. It is also important that the tape retain joint compound to avoid waste and the tedious effort of packing the entire joint with joint compound.
After the tape is applied and coated with the first coat of joint compound, a second coat of joint compound is applied. A straight edged knife is commonly used to smooth and feather the second coat of joint compound to form a uniform surface making the joint undetectable under a final coat of paint or wall paper. A section of wall, which is larger than a single sheet of wallboard will have flat joints between adjacent coplaner sheets of wallboard. Typically wallboard sheets are manufactured with tapered edges so as to form a valley at each joint, which may be filled with a quantity of joint compound allowing the volume of joint compound to form a more substantial bond. Inside corners normally have a vertical joint where sheets of wallboard lie adjacent at a ninety degree angle. Inside corners are typically taped and coated with joint compound in the same manner as flat joints. Outside corners also have a vertical joint between sheets of wallboard lying at a ninety degree angle and with an edge of one or more sheets of wallboard exposed. The exposed edge is frequently covered with a metal angle strip running from the floor to the ceiling. The angle strip is attached to the wallboard with nails. The spine of the angle strip is provided with a raised rounded bead to facilitate the application of joint compound.
Joint compound is typically applied with a straight edged knife, commonly referred to as a tape knife, by scooping a quantity of joint compound onto the knife and delivering the joint compound to the area of wall to be coated. A user manipulates the knife by moving the knife along the joint with a leading edge slightly displaced from the wall and a trailing edge contacting the wall to spread joint compound along the joint and force joint compound into recesses in the surface of the wall. Recesses may include the joint between adjacent sheets of wallboard and depressions formed by nails used to attach the wallboard. As the knife is moved, the user must maintain some degree of displacement between the leading edge of the knife and the wall but the degree of displacement is not critical. The trailing edge of the knife must contact the wall where the feathered limit of the joint compound application is intended to blend with the surface of the wallboard and the trailing edge must be slightly displaced from the wall, in the area of the joint, where a thicker application of joint compound is desired. If the user varies the angle of the trailing edge, as the knife is moved, an undesirable undulating application of joint compound will result instead of the desired uniform feathered blend with the surface of the wallboard.
An outside corner, provided with an angle strip having a bead on the spine, is easily finished with the second coat of joint compound. The difficulty of maintaining a constant angle of the trailing edge of the knife is avoided because the bead provides a guide. The user rests the trailing edge of the knife against the bead and against the wallboard at the point intended to be the limit of feathering, for the joint compound. The bead displaces the trailing edge from the wall, in the area of the joint, and the user may apply steady pressure to maintain a consistent angle of the trailing edge throughout the movement of a full stroke of the knife. The knife will deposit a thicker application of joint compound in the area of the joint, and gradually taper the thickness to achieve a feathered blend with the wallboard. Each side of the outside corner joint may be finished in the same manner.
Inside corners and flat wall joints do not have a guide bead to position the trailing edge of the knife, for the user. Typically, professionals have developed their skill to a level so that they can maintain a constant angle of the trailing edge of the knife throughout a stroke and deposit a thicker application of joint compound in the area of a joint and uniformly taper the application to blend smoothly with the wallboard. A homeowner typically finds the task of applying the second coat of joint compound to inside corners and flat wall joints to be a tedious and time consuming job. There is a need for a guide bead which can be applied to wallboard for finishing inside corners and flat wall joints, to avoid the need for manually controlling the angle of the trailing edge of a tape knife. This need has been addressed by integrating a bead with tape, see U.S. Pat. No. 4,313,991, to Lamb. The Lamb Patent '991 discloses the use of two different tapes, one for corners and one for flat joints. This requires the user to maintain two products to complete a typical project involving both corners and flat joints. In addition, the tape includes substantial areas which are impervious to joint compound so the bond with the wallboard must be dependent upon the adhesive provided on the tape.
There is a need for a guide bead dispenser for convenient application of a single type of guide bead useful for inside corners and flat joints. There is a need for a process for finishing wallboard joints which provides a positioning guide bead for a knife applying joint compound to inside corners and to flat joints.